Epidemiological assessment and Motif Fingerprint-based Genomic
Characterization of Tilapia Lake Virus (TiLV) infection and
co-infections in Colombia
Abstract
Tilapia Lake Virus (TiLV) infection is one of the most challenging
diseases of farmed tilapia ( Oreochromis sp.) production systems
globally, however, few studies have described the epidemiology of TiLV.
Here, we assessed the TiLV infection’s status in Colombia Departments by
RT-PCR amplification of a pool of tissues (liver, spleen, eye, and
brain) collected from units of five to ten tilapias per lot/pond. From
June 2016 to March 2018, epidemiological assessments of TiLV infection
found positive cases of TiLV from 109 out of 463 submitted samples
(23%) representing 25 TiLV positive farms, 21 districts, and 13
departments. Spatial distribution of cases indicate that the disease is
widespread in Colombia including 21 TiLV positive municipalities out of
29 sampled (72,4%). Segment 6 of Colombian TiLV showed 98 to 100% of
sequence identity to the viruses previously reported from Ecuador,
Israel, and Peru. Almost all cases of TiLV (103/109; 94.5%) were
associated to mortalities and clinical signs attributed to the disease
and were reported at any life stages of tilapia. Six additional cases
(5,5%) were reported from apparently healthy alevins at three
Epidemiological Units (EU). Among the 109 cases, 44 cases (40.4%) had
concomitant TiLV infection with other bacterial and/or parasitic
diseases, highlighting the complex interactions between the virus and
other pathogens. Grouping tests such as histopathology and molecular
techniques, may be able to improve the detection of moribund and
apparently healthy TiLV cases. This study, TiLV was reported throughout
Colombia as the first comprehensive epidemiological investigation of
TiLV status in South America.